I'm guessing you have one of the starforce copies of SH3. Not my area of expertise but you might have some luck on the SH3 forum, if memory serves there was a topic over there covering most win7 issues.
http://www.subsim.com/radioroom/showthread.php?t=162165
There it is. Stickied on the main page of the Sh3 general forum.
Myself, I'm lucky. I've got it running perfectly from just a straight up install and GWX install.